Booting using a single Flash Drive

Most of the bootable ISOs I have from numerous programs that are intended for different uses are convertible to a flash drive image that is bootable and can boot up with no hassles. What just bugs me a little is that having a separate flash drive or CD individually for each of the program causes hassle. Since the spaces for storage in the flash drives is not enough.The bootable programs are now stored using a 4GB memory stick. Would it be possible for all these programs to be combined into one and for a user to be allowed to boot using a single FD and still can see the different programs ?
